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2 Acta Chromatographica

2 2024

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Design of experiments and Derringer’s desirability function in optimisation and validation of RP-HPLC method for the analysis of enrofloxacin and its impurities

Dokmanovic Jelena, Kasagic-Vujanovic Irena, Gagic Žarko, Nikolic Katarina, Carapic Marija, Agbaba Danica

Acta Chromatographica

2024

Vol. 36, no. 2

132--142

Using the Design of Experiments methodology (Response-Surface Methodology and Derringer’s Desirability Function), a simple, fast and robust RP-HPLC method was developed for the analysis of enrofloxacin (EFC), its impurity A (fluoroquinolonic acid, FQ) and impurity B (ciprofloxacin, CPX). Gradient elution of samples was performed on a Zorbax Eclipse XDB C18 column (15034.6 mm, 3.5 μm) with a mobile phase consisting of 32mM phosphate buffer pH 3.5 – methanol (0 min-19.6% methanol; 15.5 min-19.6% methanol; 29.5 min-80% methanol; 30 min-19.6% methanol; 35 min-19.6% methanol), delivered at a flow rate of 1.5 mL min1, wavelength of detection 278 nm (for EFX and CFX) and 265 nm for FQ. A good linear response was achieved in the range 15–35 μgmL1 (EFX) and LOQ150% for impurities (CFX and FQ). Other validation parameters were also tested: precision, accuracy, sensitivity and robustness. The developed method was shown to be simple, practical and suitable for the analysis of EFC and its impurities (CPX, FQ) in veterinary drugs.

Analysis of scopolamine and its related substances by means of high-performance liquid chromatography

Obradovic Darija, Pešic Ivana, Carapic Marija, Lazovic Saša, AGBABA Danica

Acta Chromatographica

2024

Vol. 36, no. 2

125--131

The retention behaviour of scopolamine (hyoscine) and its related compounds (norhyoscine, atropine, homatropine, and noratropine) was investigated on the silica-based HPLC stationary phase. The retention of investigated tropane alkaloids was interpreted by using the Soczewinski-Wachtmeister equation. A high correlation between the retention parameter (log k) and lipophilicity (log P) (R 5 0.9923) confirms the significant influence of hydrophobic interactions on the retention behaviour of the aforementioned compounds. It was found that by increasing the acetonitrile fraction, a decrease in retention of the more polar epoxide derivatives (scopolamine, norhyoscine) and an increase in retention of the more lipophilic derivatives (atropine, noratropine, homatropine) is obtained. The best separation of the tropane alkaloids was achieved by a simple procedure that involved a mobile phase composed of acetonitrile and 40mM ammonium acetate/0.05% TEA, pH 6.5; 50:50 v/v. Selected conditions were assumed for the determination of scopolamine hydrochloride in the eye drops (Scopolamini hydrobromidum 0.25%). The method was validated and it was found as selective, sensitive, precise, accurate, and robust for the further qualitative analysis of the scopolamine-related compounds.